The distribution of tritium-labelled prostaglandin E(1) injected in amounts sufficient to produce central nervous effects in cats and chicks.

1. After injection of tritiated prostaglandin E(1) into the lateral cerebral ventricle, the carotid and vertebral arteries and the aorta in cats, only a small proportion of the radioactivity was recovered from the central nervous system.2. Similar results were obtained when the prostaglandin was given intra-venously and intra-arterially to chicks.3. The results of this study confirm work in other species (Hansson & Samuelsson, 1965; Samuelsson, 1964, 1965) and suggest that prostaglandin E(1) exerts its central pharmacological actions in small concentrations.